Bump ajv from 6.12.0 to 6.12.2
Bump ajv from 6.12.0 to 6.12.2

Bumps [ajv](https://github.com/epoberezkin/ajv) from 6.12.0 to 6.12.2.
- [Release notes](https://github.com/epoberezkin/ajv/releases)
- [Commits](https://github.com/epoberezkin/ajv/compare/v6.12.0...v6.12.2)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
schul-cloud/schulcloud-server,schul-cloud/schulcloud-server,schul-cloud/schulcloud-server